The way I got involved in building cheap exhibits was that when I worked as a museum educator at the Acton Science Discovery Museum, out of necessity, I had to come up with workable, inexpensive ideas for exhibits, and then figure out how to build them or cajole or commission someone else to do it.

One of my favorite "cheap" exhibits is the liquid crystal wall. I got the idea for it by playing with a liquid crystal postcard that I found at a bus stop. By the time the bus came, I wanted to have hundreds of postcards so I could leave the heat image of my whole body instead of just my handsort of like the frozen shadows exhibits. I also wanted something else to make heat images with besides my body, so I fooled with hairdryers to make them shoot out air at the right temperature for the liquid crystal sheets.

Liquid Crystal WallDescription
Liquid crystals change color over a specific range of temperatures. As the heat expands and twists the molecules in the liquid crystal film, the wavelengths of light they reflect change from red through orange, yellow, green, and blue. If you choose a temperature range between 25 and 30 degrees centigrade, you can use your body to leave colorful impressions like hand, foot, or ear prints, and you can "paint" on the film with easily modified hairdryers.

The film will hold an image for a fairly long period of time if it is mounted on an insulating material like foam. If you mount the film on a more conductive surface like wood or metal, the image will dissipate quickly. You may want to experiment with a combination of effects, but I will describe how to build a foam-backed wall below.

Things to Keep in Mind
There are several concerns with this exhibit. The first is that the hairdryers that work well keep going in and out of stock so you have to keep experimenting with them. At the time of writing (1995), my favorite was the ConAir EURO SALON 1600, available at fine drugstores everywhere. You can still epoxy the heat settings in place, and this model has a detachable lint screen in the back. The second is that the liquid crystal sheets only come on 12-inch-wide rolls, so if you want one that is four feet wide, you have to seam four sheets together. We had a commercial photography company cut, seam, mount onto foam, and front surface laminate the sheets together with a thin matte laminant which let the heat through and protected the surface. This cost more than the liquid crystal sheets, but seemed worth it because it held up for three years without a problem. Finally, to prevent the laminant from getting scratched by the ends of the hairdryer tubes, we applied fuzzy velcro to them.

Two companies that sell liquid crystal films:

Liquid Crystal Technology, Hallcrest Products, Inc.

Davis Liquid Crystal.

There are many other things to do with this material, exhibitwise. Some thoughts are to use stencils, to back the film with materials that have different thermoconductivities, to use the liquid crystal paint on materials that are not flat, etc.

Instructions
Cut your ensulite to size and lay flat on a floor or table. Cut the tape to size and unpeel the protective plastic from two of the corners a couple of inches. Apply the tape to the foam evenly by lining up the corners and unpeeling the protective plastic a little at a time while smoothing out the top of the tape as you go. Unpeel the plastic protection from the the other side of the tape and slowly apply the liquid crystal sheet in the same way. Do this carefullythere is no going back if you make a mistake!

Once the liquid crystal film is mounted on the foam, you can mount it on the wall. You can also mount the foam onto wood with double-sided tape and then screw the wood into the wall.

We chose to build a 4 x 4 foot wall. To do this, we had to attach several sheets of liquid crystal film together in seams, and then had to have the front surface of the whole piece laminated with a thin matte finish to keep the pieces from being pried apart. This was effective, but expensive. A commercial photography company did all the seaming and mounting for us which cost more than the liquid crystal film itself. We also have several smaller liquid crystal pieces in the gallery which we mounted ourselves. Commercial photography studios may also be a good source for donations of double-sided tape.

Materials for a Modified Hairdryer:
Hairdryer with a "cool" settingset the dryer on cool and drip epoxy on the switch to keep it there! (ConAir EURO SALON 1600 hairdryer works well)
An empty caulking tube with the nozzle cut off
Wide strip of fuzzy velcro
Plastic tape

Caulking tubes fit the ends of hairdryers perfectly. Attach them with tape. When you cut off the nozzle and set the hairdryer on cool, the resulting temperature is about 35-40 degrees and will be able to run all day without overheating. We got empty caulking tubes from a hardware store, so we didn't have to empty them. You can actually use any kind of tube if it fits and the hole is about 5/8 inch in diameter.

The "fuzzy" velcro is for scratch-proofing the caulking tube. Put a circle of velcro around the front of the tube to make it able to rub without problems.

You can use the hairdryers to draw pictures by moving slowly, or you can make images by using stencils. Our wall has lasted 3 years without incident, except that the dryers have a 6-12 month lifespan (keep the lint screens clean!).

We have built two small holders on the wall for the hairdryer. They look like wooden basketball hoops without nets.

Finally, the area must be well lit, preferably with incandescent lights that are bright, but not so hot as to activate the crystals and color the wall.